234 



INTESTINAL DIGESTION. 



whole of the small intestine ; although the fibres are most abundant in the 

 duodenum. The internal layer of fibres is considerably thicker than the 



longitudinal layer. These 

 fibres encircle the tube, 

 running generally at right 

 angles to the external layer, 

 but some of them having 

 rather an oblique direction. 

 The circular layer is thick- 

 est in the duodenum, di- 

 minishing gradually in 

 thickness to the middle of 

 the jejunum, but afterward 

 maintaining a nearly uni- 

 form thickness throughout 

 the canal, to the ileo-caecal 

 valve. 



The jejunum, the sec- 

 ond division of the small 

 intestine, is continuous 

 with the duodenum. It 

 presents no well marked 

 line of separation from the 

 third division, but is gen- 

 erally considered as in- 

 cluding the upper two- 

 fifths of the small intes- 

 tine, the lower three-fifths 

 being called the ileum. It 



FIG. 66. Stomach, liver, small intestine etc. (Sappey). J^<j,s received the name 16- 



1, inferior surface of the liver ; 2, round ligament of the liver ; 3, 



gall-bladder ; 4, superior surface of the right lobe of the liver ; lunum f rom the tact that 

 5, diaphragm ; 6, lower portion of the oesophagus ; 7, stomach ; . 



8. gastro-hepatic amentum : 9, spleen ; 10, gastro-splenic omen- it IS almost always lOUnd 

 turn ; 11, duodenum ; 12, 12, small intestine ; 13, ccecum ; 14, , , 



appendix vermiformis ; 15, 15, transverse colon ; 16, sigmoid empty alter death. 

 flexure of the colon ; 17, urinary bladder. __, ., 



The ileum is some- 

 what narrower and thinner than the jejunum, otherwise possessing no 

 marked peculiarities except in its mucous membrane. This division of the 

 intestine opens into the colon. 



Mucous Membrane of the Small Intestine. The mucous coat of the small 

 intestine is somewhat thinner than the lining membrane of the stomach.. 

 It is thickest in the duodenum and gradually becomes thinner toward the 

 ileum. It is highly vascular, presenting, like the mucous membrane of the 

 stomach, a great increase in the quantity of blood during digestion. It has a 

 peculiar soft and velvety appearance, and during digestion it is of a vivid- 

 red color, being pale pink during the intervals. It presents for anatomical 

 description the following parts : 1, folds of the membrane, called valvulae 

 conniventes ; 2, duodenal racemose glands, or glands of Brunner ; 3, intestinal 



